1. Field of the Invention
The present invention relates to an optical device that may be connected to an optical fiber cable and used in optical communication. In particular, the invention relates a surface-mountable optical device that may be mounted on a circuit board and assembled with other components.
2. Description of Related Art
Various optical devices and their peripheral components have been devised and developed heretofore for optical communication. One of such optical device and its peripheral components are shown in FIGS. 16 and 17.
FIG. 16 is a schematic plan view for illustrating a conventional optical device and its peripheral components and FIG. 17 is a schematic side view of the assembly where the optical device and its peripheral components are mounted on a circuit board 5.
In these figures, the reference numeral 28 denotes an optical device, 3 denotes an optical fiber cable comprising a cable wire 3a and a standard plug 3b, and 29 denotes an adaptor for optically coupling the optical device 28 and the optical fiber cable 3. The reference numeral 5 denotes a circuit board on which the optical device 28 is mounted. The reference numeral 30 is a device body 30 in which internal optical components (not shown) and the like are integrated. The reference numeral 31 denotes leads for securing the device body 30 on the circuit board 5 and electrically connecting the above optical components to external components (not shown). The reference numeral 32 denotes an optical cable protruded from the device body 30, and also 33 denotes a plug fixed on the tip of the optical cable 32.
The conventional optical device 28 and the peripheral components are assembled by: soldering leads 31 on the circuit board 5; and then coupling the plug 33 with the standard plug 3b through the adapter 29.
As the optical device is assembled as described above, there are several problems that lie within the step of mounting both the optical device and its peripheral components on the surface of the circuit board and also lie within their usage patterns.
Firstly, for a manufacturer, the conventional optical devices cannot be provided in quantity by automatically controlled manufacturing process because each of them has the optical fiber cable 32 that extends from the device body 30 irrespective of its length. For a user, the conventional optical device 28 cannot be mounted on the circuit board 5 simultaneously with other components. Thus each part of the optical device 28 needs to be manually mounted on the circuit board 5 after mounting the other components on the circuit board 5.
Secondary, most components currently available have surface-mountable leads. For the conventional optical device 28 described above, the number of terminals to be used in electrical contact between the optical device 28 and other components may be 8 to 20. Therefore, the leads are provided as through-hole leads in DIP (Dual Inline Package) in consideration of a strength of securing the optical device 28 on the circuit board 5 against, for example, pulling the optical fiber cable 32 accidentally. It means that there is no component that can be installed on the backside of the circuit board 5 on which the optical device 28 is mounted, standing in the way of attaining higher packing density.
Thirdly, the required number of components is considerable. The conventional optical device 28 requires a connecting means such as the adapter 29 mentioned above for connecting the optical fiber cable 32 that extends from such a device to the standard plug 3b of another cable 3 in practical use.
To solve the above problems, several approaches have been proposed so far in the step of mounting an optical device and its peripheral components on a circuit board and the usage pattern thereof. FIG. 18 is a schematic plan view for illustrating the construction of another conventional optical device (hereinafter, referred as a second conventional optical device) and its peripheral components.
In the figure, the reference numeral 34 denotes a ferrule protruding from one end of the device body 30 in which an optical fiber (not shown) is coaxially provided. The reference numeral 35 denotes an optical fiber cable designed specifically for the device body 30. The optical fiber cable 35 comprises a cable wire 36, a ferrule 37, and a plug 38. The reference numeral 39 denotes a sleeve for positioning the ferrule 37 of the specific optical cable 35 and the ferrule 34 of the device body 30 together with great precision. The reference numeral 29 denotes an adaptor for optically coupling between the plug 38 and the standard plug 3b. 
In addition, the reference numeral 41 denotes a female connector fixed on the device body 30, and 42 denotes a male connector which is provided around the ferrule 37.
Accordingly, the optical device and its peripheral components are constructed as described above, so that the optical device can be configured in which the optical fiber cable 35 extends from the surface of the device body 30 by mounting the device body 30 on a circuit board (not shown in FIG. 18) and then coupling the connectors 41, 42 together through the sleeve 39.
The second conventional optical device is designed so that the optical fiber cable 35 does not extend from the device body 30 in itself. Thus, the device body 30 can be automatically mounted on the substrate 5 together with other components by means of batch reflowing.
In spite of the improved configuration of the second conventional optical device, a sufficient strength securing the device 28 on the circuit board 5 against an externally applied force caused by mating and unmating of the optical fiber cable 3 cannot be ensured. Notably, an insufficient securing strength becomes increasingly serious if surface-mountable leads are used. Thus, the second conventional optical device requires through-hole leads. In this case, however, it stands in the way of attaining simultaneous mounting with other components and higher packing density.
Furthermore, the second conventional optical device cannot attain a sufficient securing strength against an externally applied force caused by directly mating and unmating the standard plug 3b of the optical fiber cable 3 with the optical device. Thus, the device body 30 should be connected to the specific optical fiber cable 35, followed by connecting such a cable 35 to the standard plug 3b of the optical fiber cable 3. As a result, the number of components required increases considerably.
Therefore, an object of the present invention is to provide a surface-mountable optical device which can be installed on a circuit board simultaneously with other components by means of surface-mount technology and directly connecting to a standard plug of an optical fiber cable for simultaneously attaining the reduction in component count and an increased packaging density.
In the first aspect of the invention, there is provided a surface-mountable optical device comprising:
an optical component unit having a package, an inner optical components installed in the package, a plurality of surface-mountable leads protruded from the package, and a ferrule optically coupled to the inner optical components and protruded from the package in a predetermined direction; and
a receptacle unit having a receptacle for holding an optical fiber cable to ensure an optical coupling between the optical fiber cable and the ferrule, and a plurality of surface-mountable leads fixed on the receptacle,
wherein
the surface-mountable optical device and the receptacle unit are provided independently, and the receptacle unit is inserted into the surface-mountable optical unit along the predetermined direction.
Here, the receptacle unit may be formed to ensure the optical coupling between the optical fiber cable and the ferrule when a space between an outermost surface-mountable lead of the optical component unit on the ferrule side and an outermost surface-mountable lead of the receptacle unit on the optical component unit side, which are adjacent to each other, is an integral multiple of a space between the adjacent surface-mountable leads of the optical component unit.
A width of the surface mountable lead of the receptacle units may be larger than a width of the surface mountable lead of the optical component unit.
A length of the surface mountable lead of the receptacle units may be smaller than a length of the surface mountable lead of the optical component unit.
The optical component unit may further comprise at least one guide portion formed from a molding resin and protruded therefrom in the direction coincided with the predetermined direction, for moving the receptacle unit along the guide portion to make an insertion of the receptacle unit into the optical component.
The optical component unit may further comprise at least one guide portion formed from the lead frame and provided thereon in the direction parallel to the predetermined direction, and the receptacle unit may further comprise at least one slit to be fit to the guide portion.
One of the optical component unit and the receptacle unit may have at least one recess or through hole being opened in a direction perpendicular to a predetermined direction, while the other of the optical component unit and the receptacle unit may have at least one protrusion at a position facing to the recess or through hole when the receptacle unit is inserted into the optical component unit.
In a second aspect of the present invention, there is provided a surface-mountable optical device assembly comprising:
a surface-mountable optical device, a circuit board on which the surface-mountable optical device is mounted, and an optical fiber to be optically connected to the surface-mountable optical device, wherein
the surface-mountable optical device is comprised of:
an optical component unit having a package, inner optical components installed in the package, a plurality of surface-mountable leads protruded from the package, and a ferrule optically coupled to the inner optical components and protruded from the package in a predetermined direction; and
a receptacle unit having a receptacle for holding an optical fiber cable to ensure an optical coupling between the optical fiber cable and the ferrule, and a plurality of surface-mountable leads fixed on the receptacle, wherein
the surface-mountable optical device and the receptacle unit are provided independently, and the receptacle unit is inserted into the surface-mountable optical unit along the predetermined direction.